A while ago some might remember me mentioning here that an elderly neighbour we keep an eye on was finding heating on when she only wanted hot water. I believe the diagnosis was the rubber ball in the motorised valve was allowing water past into the CH cct when in the HW position and I bought a new valve ready.
She was happy to just use immersion for HW so I thought we'd wait till it was a little bit cooler in the loft and in general before doing the job.
She mentioned to the Mrs earlier that it was starting to get a bit cooler and so I just popped over to swap her back to the gas boiler and re-set the timer to get things flowing again and whilst it looks and sounds like it's trying to spark up, it's not managing to?
We have the water pump running (checked via the spindle cover), the boiler fan, the igniter bit it looks like it might fire up a pilot > flame failure detector > main burner but isn't getting the pilot, if that's actually what happens. If it should light the main burner directly from the igniter it's not doing that either. 
I can't smell any gas on the outside but I can feel reasonable airflow.
Turn the main boiler knob to off, leave it a few seconds, turn it back on again, and you hear the fan come on, then after a few seconds delay, a fairly loud 'clunk' (gas valve?) and then the igniter starts going but that's it? She has gas on the hob nearby.
Anyone had / got one and can remember the fire up sequence or can offer any other thoughts please?
I've swapped her back to the immersion heater for tonight and can have a closer look in the morning.
Cheers, T i m
 If you peer into the boiler though the spy hole and watch carefully, every 3 or 4 sparks it looks like it is surrounded by a tiny flame but as if it's blown out before it can build up?